The subjective fear and the physical danger of carcinogenic and mutagenic substances in the environment are subjects for public discussion and raise difficult regulatory problems of balancing industrial need and public health. The problem of regulation is compounded by the empirical nature of the subject. Mutagenic and carcinogenic substances can be identified and many compounds have both properties but understanding the basic science of why this is so and how the phenomena come about is still limited. Happpily we see a blossoming interdisciplinary effort which is providing important new information on the basic biological and chemical mechanisms involved in mutagenesis and carcinogenesis. We believe that discussion of the interaction of mutagenic and carcinogenic processes at a basic level can have important practical consequences. Understanding the how and why can simplify the regulatory problem. A Gordon Conference should be perfect for such a discussion. We hope that a meeting following the Gordon Conference rules should permit precise formulation of profitable research directions. The following sessions are planned (Session Chairman's name in parenthesis): Mutagenesis: Biological Analysis (John Drake); Mutagenesis: Chemical Analysis (Dezider Grunberger); Carcinogenesis: Cell Transformation and Inhibitors (I. Bernard Weinstein); Carcinogenesis: Biochemistry of Transformation (Paul Ts'o); Inducible Repair Systems (Bernard Strauss); Specific Repair Enzymes (Erroll Freidberg and Stuart Linn); Parameters of Base Pairing in Transcription and Translation (Bea Singer); Hazards and Regulations: Carcinogenic and Mutagenic Agents (David Rall). The Conference is scheduled for July 14-18, 1980 in New Hampshire.